1. Field of the Invention
The present invention relates to a vehicle drive assist system that assists driving by assisting steering with reference to a traveling lane and a preceding vehicle.
2. Description of the Related Art
In recent years, drive assist systems have been developed and used practically. In drive assist systems, a traveling environment in front of a vehicle is detected, for example, by a camera mounted in the vehicle. On the basis of data on the traveling environment, a traveling lane and a preceding vehicle are detected, and driving is controlled along the traveling lane or while following the preceding vehicle.
For example, Japanese Unexamined Patent Application Publication No. 2003-81123 discloses a vehicle steering control system in which a traveling lane is detected and a vehicle is caused to run along the traveling lane. In this system, a target yaw rate is calculated from the lateral displacement of a forward gazing point, the vehicle speed, and the forward-gazing-point distance, and a steering torque is generated so that the calculated target yaw rate can be obtained.
However, in the steering control system disclosed in the above publication, control is performed so as to obtain the target yaw rate calculated from the lateral displacement of the forward gazing point, the vehicle speed, and the forward-gazing-point distance. Therefore, control is constrained by the balance among these parameters, and this may hinder natural control. For example, while it is sometimes natural that running is performed along the traveling lane, it is sometimes natural that running is performed while following the preceding vehicle. Further, when both the traveling lane and the preceding vehicle are recognized, it is important to determine the balance therebetween.